Process for manufacture of lubricating oil

ABSTRACT

A stabilized lubricating oil having acceptable corrosion properties and being resistant to oxidation and sludge formation upon exposure to an oxidative environment is prepared without forming undesirable color bodies therein by the sequential steps of: A. CONTACTING THE LUBRICATING OIL STOCK WITH A SMALL AMOUNT OF ELEMENTAL SULFUR OF FROM ABOUT 0.05 TO ABOUT 1.0 PERCENT BY WEIGHT AT A CONTACT TEMPERATURE OF FROM ABOUT 25*C to about 130*C, b. contacting the product oil of step (a) with from about 10 to about 50 weight percent sulfide-forming metal at a contact temperature of from about 25*C to about 150*C, and C. SEPARATING THE PRODUCT OIL OF STEP (B) FROM THE METAL SULFIDE-CONTAINING RESIDUE THEREIN FORMED.

i United States Patent [1 1 Scott et a1.

[ PROCESS FOR MANUFACTURE OF LUBRICATING OIL [75] Inventors: Eric J. Y. Scott, Princeton; Robert L. Smith, Hopewell, both of NJ.

[73] Assignee: Mobil Oil Corporation, New York,

[22] Filed: Aug. 8, 1974 [21] Appl. No.: 495,593

[52] U.S. Cl 208/293; 208/251 R; 208/253 [51] Int. Cl. C10G 21/10; C10G 29/04 a [58] Field of Search 208/293, 251, 253, 88

[56] References Cited UNITED STATES PATENTS 2,790,751 4/1957 Gerald 208/253 2,854,399 9/1958 Weller 208/293 3,245,892 4/1966 Jones 204/158 S 3,849,297 l1/l974 Long 208/25] R FOREIGN PATENTS OR APPLICATIONS 699,206 10/1940 Germany 208/293 1 Nov. 4, 1975 Primary Examiner-Delbert E. Gantz Assistant Examiner-Juanita M. Nelson Attorney, Agent, or Firm-Charles A. Huggett; Raymond W. Barclay; Dennis P. Santini ABSTRACT A stabilized lubricating oil having acceptable corrosion properties and being resistant to oxidation and sludge formation upon exposure to an oxidative envi ronment is prepared without forming undesirable color bodies therein by the sequential steps of:

17 Claims, No Drawings PROCESS FOR MANUFACTURE OF LUBRICATING OIL CROSS'REFERENCE TO RELATED APPLICATION Application Ser. No. 495,591, filed on the same date herewith, is directed to treatment of lubricating oil stock with elemental sulfur followed by removal of unreacted sulfur therefrom.

BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to the production of improved lubricating oils. In particular, it relates to the preparation of stable lubricating oils having acceptable corrosion properties without sacrifice in color which are highly resistant to oxidation and sludge formation when exposed to a highly oxidative environment.

2. Description of Prior Art Hydrocarbon lubricating oils have been obtained by a variety of processes in which high boiling fractions are contacted with hydrogen in the presence of hydrogenation-dehydrogenation catalysts at elevated temperatures and pressures. in such processes, there is a consumption of hydrogen. Lubricating oil fractions are separated from the resulting products. Such lubricating oil fractions differ from those obtained by frac tional distillation of crude oils and the like, since they have such relatively high viscosity index values that sol vent extraction treatments are generally not required to enhance their viscosity index values. Such lubricating oil fractions suffer from the shortcoming that they are unstable when exposed to highly oxidative environments. When so exposed, sediment and lacquer formation occurs, thus lessening the commercial value of such lubricants.

Methods in the art directed to lessening such a shortcoming are examplified by U.S. Pat. Nos. 3,436,334 and 3,530,061. They teach making a lubricating oil product fraction of hydrocracking resistant to deterioration upon exposure to light and air by contacting the lubricating oil fraction with a solid contacting agent having hydrogenation-dehydrogenation properties under hydro pressure (U.S. Pat. No. 3,530,061); and making hydrocarbon lubricating oil resistant to such deterioration by contacting high boiling hydrocarbons with a hydrogenation-dehydrogenation catalyst and hydrogen (with hydrogen consumption), and thereafter dehydrogenating the resultant product on contact with a metal oxide or with metal and oxygen (U.S. Pat. No. 3,436,334). Both methods employ hydrogen atmosphere, high pressure and high temperature, i.e., 500 to 1,000F. No sulfur is employed in either patent method.

U.S. Pat. No. 2,914,470 is directed to hydrorefining a petroleum oil fraction by contacting it with a catalyst in the presence of hydrogen sulfide. Temperatures and pressures taught for the process of this patent are 600 to 825F and 150 psig to 3,000 psig, respectively.

U.S. Pat. No. 2,432,440 is directed to a high temperature, high sulfur treatment of lubricating oil stock to improve its oxidative stability. Also taught in the latter patent is a caustic wash method of removing unreacted sulfur from the so treated oil stock.

The present invention is directed to a process and means for effecting substantial improvement in oxidative properties of lubricating oil by a low pressure, low temperature contacting with a small amount of elemen- 2 tal sulfur in the absence of a catalyst, followed by an efficient removing of unreacted sulfur without resort to caustic treatment.

U.S. Pat. No. 2,604,438 teaches a hydroforming process for catalytic dehydrogenation of light (i.e., boiling at less than 600F) hydrocarbon oils, presumably to increase aromatic content. The patent discloses the known fact that in processes of that nature, the presence of a small amount of sulfur in the feed has a beneficial effect. It further states that when the oil to be hydroformed has no sulfur, i.e., no sulfur in the light hydrocarbon feed, then a small amount of sulfur, e.g., a reducible sulfur compound, is added to the feed. The patent emphasizes that the invention dislcosed therein is only advantageous when the process is carried out at a temperature conducive to dehydrogenation, ie, at a temperature of at least 825F,

The prior art practices of hydrofinishing and hydrotreating as a means oftreatment of hydrocarbon lubri cating oil stocks (i.e., stocks boiling at temperatures over 600F) leave behind the unstable oil fractions. i,e., hydroaromatic compounds, with labile hydrogen atoms such as, for example, fluorenes, benzofluorenes, acenaphthenes, tetralin, fused cycloalkylaromatics and naphthenes, which are quite unstable toward oxygen, particularly in the presence of metals in lubricating oil formulations containing overbased additives. These hydroaromatic compounds with labile hydrogen atoms are known to be present in small quantities in conventionally furfural refined stocks and can lead to oxidative instability of any lubricant containing them. Further, it is well known that the sensitivity of certain lubricating oils toward alkaline additives can cause oxidative degradation in applications where overbased ad ditives are used, such as automotive and diesel lubri cants. Also, metal sensitivity can be quite detrimental to the oxidative stability of lubricants or functional fluids in applications such as turbine circulating oils, steam turbine oils and hydraulic fluids. No method is known at present which so effectively and easily alleviates the above problems as the present invention.

SUMMARY OF THE INVENTION In accordance with the present inventon there is pro vided a process and means for forming lubricating oils which are highly resistant to deterioration, e.g., oxida tion and sludge formation, upon exposure to an oxidative environment.

The process of the present invention comprises contacting a lubricating oil stock, such as, for example, from a Midcontinental U.S.A. crude or an Arabian Light crude, with elemental sulfur in amount of from about 0.05 to about 1.0 percent by weight of the oil stock at a mild temperature of from about 25 to about C, contacting the product oil of said sulfur contacting step with from about 10 to about 50 weight percent sulfide-forming metal at a contact temperature of from about 25 to about C, thereby forming a metal sulfide-containing residue, and separating the product oil of said metal contacting step from the metal sulfide-containing residue therein formed.

The elemental sulfur for use herein may be provided for the process as such or generated in situ and may be provided, if desired, by a sulfur precursor, such as, for example, H 8, or an added organosulfur compound.

Non-limiting examples of sulfur precursors which may be utilized in the present process include H 5, RSH, RS H, HS H and RS R, wherein R is a hydro- 3 carbyl group and .r is an integer of from I to 4 or more.

The preferred form of sulfur for use herein is crystalline. such as that product by recrystallization of sublimed sulfur from toluene.

The sulfidc-forming metal for use herein may be any suitable metal which will readily form metal sulfide on contact with an oil containing unreacted sulfur which is free to form such as sulfide with said metal. Non-limiting examples of such metals useful herein include metals of Groups 18. IIB. IVA and VIII of the Periodic Table of the Elements. such as. for example, iron, cobalt. nickel. copper. silver. palladium, zinc, mercury, tin and lead.

Separation of the product oil of the metal contacting step of the present process for the metal sulfide-containing residue therein formed may be be accomplished by any one of several well known methods in the art. Non-limiting examples of such methods include. for example. filtration and decantation.

DESCRIPTION OF SPECIFIC EMBODIMENTS The lubricating oilstock which may be treated in accordance with the present invention may generally be any high boiling range materials boiling above about 600F. Such lubricating oil stock materials include those obtained by fractionation, as by. for example. vacuum distillation. of crude oils identified by their source. i.e.. Pennsylvania. Midcontinent, Gulf Coast. West Texas, Arnal. Kuwait, Barco and Arabian. Said oil stock material may be one having a substantial part thereof of the fractionation product of the above crude oils mixed with other oil stocks.

The elemental sulfur employed in the present process may be crystalline, amorphous or colloidal and may be any of several allotropic forms such as S S or polymeric sulfur. and maybe used in small amounts of from about 0.05 to about 1.0 percent by weight of oil stock with a preferable range of from about 0.I to about 0.5 percent by weight. It is readily observable that this in vention differs from the well-known method of making sulfurized oilextreme pressure agents in conditions of processing. the concept of improvement. the amount and type of sulfur incorporated and the chemical modification of the oil stock itself. In the present invention. small amounts of stable sulfur may possibly be chemically incorporated into the oil molecules as labile hydrogen atoms are removed. On the other hand. in sulfurized oils used as extreme pressure agents. large quanti ties of sulfur, such as. for example. 10 to l5 percent by weight. are incorporated. including a substantial quantity of elemental sulfur as such.

The operating parameters in the present process are maintained so as to achieve the desired degree of im provement or upgrading of product quality of the lubricating oil stock treated without loss in yield and without forming undesirable color bodies therein. Aside from specific small amounts of sulfur, the temperature of the sulfur-contacting step of the process must be within the range of from about 25 to about 130C. with a preferred range of from about 25 to 70C. Also, the pressure of the sulfur-contacting step of the process must be within the range offrom about psig. to about I00 psig.. with a preferred range of from about 0 psig. to about psig.

With respect to the metal-contacting step, the temperature must be maintained within the range of from about to about 150C, with a preferred range of from about to about 90C. Also. the pressure ofthe metal-contacting step of the process must be within the range of from about 0 psig. to about I00 psig., with a preferred range of from about 0 psig. to about 5 psig.

In order to more fully illustrate the process of the present invention, the following specific examples. which in no sense limit the invention. are presented. The test procedures used in evaluation of the product yield from the present process are standard tests designated ASTM: D2272- 67 (RBOT," rotating bomb oxidation stability test) and ASTM:DI3U- 6 (copper corrosion test). In the corrosion test, results are reported in the following order of severity:

IA I no corrosion I I8 lslight corrosion) 2A (more than lBl '18 (more than 2A] If [more than 28] 2D ttt u It.

EXAMPLES 1-6 The lubricating oil stock used in these examples was conventionally refined by furfural extraction and methyl ethyl ketone dewaxing. It is referred to as Arab Light stock and has the following significant properties.

Prior to testing any lubricating oil stock samples herein according to the above mentioned standard tests. they were blended with a standard additive package constituting less than one weight percent of the oil. A portion of such blended oil stock without any further treatment was set aside as base stock for comparison purposes and was designated Example l.

As Example 2, a quantity of the above oil stock was charged into an ultrasonic mixing device (1.650 watts) and contacted with 0.5 weight percent elemental sulfur (recrystallized from toluene) during ultrasonic agitation at 62C for 2 hours and under nitrogen purge.

As example 3. 240 grams of the product oil of Example 2 was weighed into a 500 ml. Erlenmeyer flask to gether with grams of sulfideforming metal from Group IB of the Periodic Table of Elements. i.e.. copper, in the form of light turnings, cut with shears to A to 1 inch lengths. The flask was stoppered with a V- groove cut in the stopper cork and placed in a con trolled temperature oven having a 380 mljminute nitrogen purge to exclude air. The metal-contacting was continued for 65.5 hours at 62C, resulting in a dark metal sulfide residue. Ninety-five grams of the product oil of the metal-contacting step was then separated from the residue by decantation and filtration.

As example 4, the Erlenmeyer flask of Example 3. containing the treated oil remaining after the 95 grams was separated, was placed in the same oven for 3 hours under an air atmosphere at l2lC. It was then removed from the oven and the remainder of the product oil of the metal-contacting step was separated from the residue by decantation and filtration.

As Example 5, another quantity of the product oil of Example 2 was weighed into a 500 ml. Erlenmeyer flask together with a sulfide-forming metal, i.e., copper, in the ratio of 4:1, oil:copper. This oilmetal mixture was then treated as in Example 3. The metal-contacting was continued for 22.2 hours at 89C. The product oil of the metal-contacting step was then separated from the metal sulfide-containing residue therein formed by decantation and filtration.

As example 6, a further quantity of the product oil of Example 2 was washed with 20 percent aqueous NaOH solution (containing 0.6 weight percent sodium sulfide nonahydrate) and then with percent aqueous NaCl solution until the aqueous layer had a pH of 7 and then with distilled water until the aqueous layer was free of chloride ions as measured by the AgNO test. During the entire caustic wash of this example, the temperature was maintained at 70C or less.

The final product oil of each example, following blending with the standard additive package, was then tested in the above-mentioned RBOT and corrosion tests. The results of those tests appear in Table 2.

It is observed from the results of the foregoing examples, especially from comparison of Examples 3 and 6, that the present process provides a stabilized lubricating oil having acceptable corrosion properties which is resistant to oxidation and sludge formation upon exposure to an oxidative environment.

It is further interesting to note that the present process has the important advantage over processes including a caustic was that there is no water-alkali or water washing needed. This fact reduces refinery pollution problems associated with caustic disposal. The metal sulfides formed during this process may be, if desired, regenerated, possibly by a mild oxidation followed by reduction to metal for reuse herein.

Having thus given a general description of the process and means of this invention and provided by way of examples spepcific embodiments thereof, it is to be understood that no undue restrictions are to be imposed by reason thereof, and minor modifications may be made thereto without departing from the scope thereof.

What is claimed is:

l. A process for forming a stabilized lubricating oil having acceptable corrosion properties and being resistant to oxidation and sludge formation upon exposure to an oxidative environment which comprises the sequential steps of (a) contacting a hydrocarbon lubricating oil stock with elemental sulfur in an amount offrom about 0.05 to about 1.0 percent by weight of said oil stock at a contact temperature of from about 25 to about 130C and pressure of from about 0 psig to about 100 psig, (b) contacting the product oil or step (a) containing unreacted sulfur with from about [0 to about 50 weight percent sulfide-forming metal at a contact temperature of from about 25 to about 150C and pressure of from about 0 psig to about 100 psig, thereby forming a metal sulfide-containing residue, and (c separating the product oil of step (b) from the metal sul fide-containing residue therein formed.

2. The process of claim I wherein said contacting step (a) is accomplished in an ultrasonic bath.

3. The process ofclaim 1 wherein said elemental sulfur is present in step (a) in an amount offrom about 0.1 to about 0.5 percent by weight of said oi] stock and said contact temperature in step (a) is from about 25 to about C.

4. The process of claim 1 wherein said sulfide-forming metal of step (b) is selected from the group consisting of metals ofGroups [8, NB, [VA and VIII of the Periodic Table of the Elements.

5. The process of claim 3 wherein said sulfide-forming metal of step (b) is selected from the group consisting of metals of Groups I8, I18, [VA and VII] ofthe Periodic Table of the Elements.

6. The process of claim 1 wherein said contact temperature in step (b) is from about 35 to about C.

7. The process of claim 1 wherein said elemental sulfur in step (a) is provided by an added sulfur precursor.

8. The process of claim 7 wherein said sulfur precursor is one selected from the group consisting of H 5, HRS, RS H. HS,H and RS R, wherein R is a hydrocarbyl group and x is an integer of from l to 4 or more.

9. The process of claim 1 wherein said elemental sulfur in step (a) is provided by one or more added or gano-sulfur compounds.

10. The process of claim I wherein said elemental sulfur in step (a) is crystalline.

H. The process of claim 10 wherein said crystalline sulfur is obtained by recrystallization of sublimed sulfur from toluene.

12. The process of claim 1 wherein said oil stock has a boiling range above about 600F.

13. The process of claim 12 wherein said oil stock comprises at least a substantial part of one obtained by fractionation of a crude oil identified as Pennsylvania, Midcontinent, Gulf Coast, West Texas, Amal, Kuwait, Barco or Arabian.

14. The process of claim 13 wherein said oil stock is one obtained by fractionation of crude oil identified as Arabian.

IS. The process of claim 1 wherein said sulfide-forming metal in step (b) is copper.

16. the process of claim 5 wherein said sulfide-forming metal in step (b) is copper.

17. The process of claim 6 wherein said sulfide-forming metal in step (b) is copper.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3, 917,566 DATED Novemberi, 1975 INVENTOR(S) ERIC J. Y. SCOTT and ROBERT L. SMITH- It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line N 8 "inventon" should read -invention. Column 3, line 16 "may be be" should read -may be-. Column 6, line 10 "or" should read of-.

(Claim 1) Signed and Scaled this Twenty-fourth D ay 0f January 1978 [SEAL] RUTH C. MASON LUTRELLE F. PARKER Arresting Officer Acting Commissioner of Patents and Trademarks 

1. A PROCESS FOR FORMING A STABILIZED LUBRICATING OIL HAVING ACCEPTABLE CORROSION PROPERTIES AND BEING RESISTANT TO OXIDATION AND SLUDGE FORMATION UPON EXPOSURE TO AN OXIDATIVE ENVIROMENT WHICH COMPRISES THE SEQUENTIAL STEPS OF (A) CONTACTING A HYDROCARBON LUBRICATING OIL STOCK WITH ELEMENTAL SULFUR IN AN AMOUNT OF FROM ABOUT 0.05 TO ABOUT 1.0 PERCENT BY WEIGHT OF SAID OIL STOCK AT A CONTACT TEMPERATURE OF FROM ABOUT 25* TO ABOUT 130*C AND PRESSURE OF FROM ABOUT 0 PSIG TO ABOUT 100 PSIG, (B) CONTACTING THE PRODUCT OIL OR STEP (A) CONTAINING UNREACTED SULFUR WITH FROM ABOUT 10 TO ABOUT 50 WEIGHT PERCENT SULFIDE-FORMING METAL AT A CONTACT TEMPERATURE OF FROM ABOUT 25* TO ABOUT 150*C AND PRESSURE OF FROM ABOUT 0 PSIG TO ABOUT 100 PSIG, THEREBY FORMING A METAL SULFIDE-CONTAINING RESIDUE, AND (C) SEPARATING THE PRODUCT OIL OF STEP (B) FROM THE METAL SULFIDE-CONTAINING RESIDUE THEREIN FORMED.
 2. The process of claim 1 wherein said contacting step (a) is accomplished in an ultrasonic bath.
 3. The process of claim 1 wherein said elemental sulfur is present in step (a) in an amount of from about 0.1 to about 0.5 percent by weight of said oil stock and said contact temperature in step (a) is from about 25* to about 70*C. .
 4. The process of claim 1 wherein saidi sulfide-forming metal of step (b) is selected from the gorup consisting of metals of Groups IB, IIB, IVA and VIII of the Periodic Table of the Elements.
 5. The process of claim 3 wherein said sulfide-forming metal of step (b) is selected from the group consisting of metals of Groups IB, IIB, IVA and VIII of the Periodic Table of the Elements.
 6. The process of claim 1 wherein said contact temperature in step (b) is from about 35* to about 90*C.
 7. The process of claim 1 wherein said elemental sulfur in step (a) is provided by an added sulfur precursor.
 8. The process of claim 7 wherein said sulfur precursor is one selected from the group consisting of H2S, HRS, RSxH, HSxH and RSxR, wherein R is a hydrocarbyl group and x is an integer of from 1 to 4 or more.
 9. The process of claim 1 wherein said elemental sulfur in step (a) is provided by one or more added organo-sulfur compounds.
 10. The process of claim 1 wherein said elemental sulfur in step (a) is crystalline.
 11. The process of claim 10 wherein said crystalline sulfur is obtained by recrystallization of sublimed sulfur from toluene.
 12. The process of claim 1 wherein said oil stock has a boiling range above about 600*F.
 13. The process of claim 12 wherein said oil stock comprises at least a substantial part of one obtained by fractionation of a crude oil identified as Pennsylvania, Midcontinent, Gulf Coast, West Texas, Amal, Kuwait, Barco or Arabian.
 14. The process of claim 13 wherein said oil stock is one obtained by fractionation of crude oil identified as Arabian.
 15. The process of claim 1 wherein said sulfide-forming metal in step (b) is copper.
 16. the process of claim 5 wherein said sulfide-forming metal in step (b) is copper.
 17. The process of claim 6 wherein said sulfide-forming metal in step (b) is copper. 